This invention can be used in various fields where constructions are tested for continuity defects in not-so-easily accessible areas; examples of technology implementation may include pipes for oil and gas industry, detection of flaws in rolled products in metallurgical industry, welding quality of heavy duty equipment such as ships and reservoirs, etc. It is especially important for loaded constructions, such as pressured pipes, infrastructure maintenance, nuclear power plant monitoring, bridges, corrosion prevention and environment protection.
Similar to the modes of transportation like roads, railroads, and electric transmission lines, the pipelines have an important role in the nation's economy, belonging to the long linear assets. They typically cross large distances from the points of production and import facilities to the points of consumption. Like the other modes of transportation, pipelines require very large initial investment to be built, having long exploitation periods when properly maintained. Like any engineering structure, pipelines do occasionally fail. While pipeline rates have little impact on the price of a fuel, its disruptions or lack of capacity can constrain supply, potentially causing very large price spikes. That's why pipelines, such as ones used in the oil and gas industry, require regular inspection and maintenance before potentially costly failures occur.
The major causes of pipeline failures around the world are external interference and corrosion; therefore, assessment methods are needed to determine the severity of such defects when they are detected in pipelines. Pipeline integrity management is the general term given to all efforts (design, construction, operation, maintenance, etc.) directed towards ensuring continuing pipeline integrity.
A traditional method of assessing the structural integrity is typically complemented by flaw detection using in-line inspection (ILI), detecting and evaluating various metal defects organized by area (clusters), assessing their danger by calculating a level of stress-deformed state (SDS), and deciding on a permissible operating pressure with evaluated factor of repair (EFR), based on residual pipe wall thickness (for defects of “metal loss”—corrosion type).
As a contact technique, pigging has been used for many years to maintain larger diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging systems is increasing in many plants as plant operators search for increased efficiencies and reduced costs. Unfortunately, the ILI using intelligent pigging is unavailable for a wide range objects that require full disruptive inspection and significant spending on repair preparation. While the ILI method is suitable for the initial flaw detection, it is less efficient for the relative degree (ranking) of the risk-factor evaluation, as well as for defective pipeline serviceability calculation.
Pipe-line pigging can detect the following types of defects: i) changing in geometry: dents, wavy surface, deformed shape of cross-section; ii) metal loss, having mechanical, technological or corrosion nature; material discontinuity: layering and inclusions; iii) cracks; iv) all types of welding defects.
Pipe-line pigging is a very expensive and labor-consuming method. The major limitation of this method is the fact that a large part of pipe-lines are not prepared to be used, e.g. due to lack of input/output chambers for pig-flow device launching and pipe-line cleaning access, partially blocked pipe cross-section due to the welding artifacts, geometrical abnormalities and large slopes (small radius turns) of the pipe-line layout. In order to make the pipe-line pigging method possible, a significant preparation has to be done in advance, in particular, the high residual level magnetization (saturated magnetic fields) of the pipe-line has to be performed before using the pig-flow device. This causes future technical problems of the pipeline demagnetization that required for actual pipe repair after the pigging.
Moreover, the evaluation of the absolute values of mechanical flaws by pigging is particular difficult due to the multiple additional factors that have to be taken into account, e.g. bearing capacity of the soil, local cyclical loads (temperature, etc.).
Typically, a pipeline company will have a thorough pipeline safety program that will include a routine for the identification of pipeline defects and review of pipeline integrity. Such a plan should include, but not be limited to: i) a review of previous inspection reports by a third party expert; ii) excavation of sites identified by this review for visual examination of anomalies; iii) repairs as necessary; and iv) addressing factors in the failure and verify the integrity of the pipeline.
It is important to mention that the pipeline safety program can be only as effective as the interpretation of internal inspection reports.
There are several methods for integrity assessment of extended structures (e.g. metallic pipes) that have been proposed in literature. Thus, U.S. Pat. No. 4,998,208 (Buhrow, et al) discloses the piping corrosion monitoring system that calculates the risk-level safety factor producing an inspection schedule. The proposed system runs on a personal computer and generates inspection dates for individual piping elements. Corrosion data for individual inspection points within each circuit is used to estimate likely corrosion rates for other elements of the particular circuit. It translates into risk factors such as the toxicity, the proximity to the valuable property, etc. The system evaluates a large number of possible corrosion mechanisms for each inspection point providing a very conservative inspection date schedule.
There is another method disclosed in U.S. Pat. No. 6,813,949 (Masaniello, et al.), which addresses a pipeline inspection system having a serviceability acceptance criteria for pipeline anomalies, specifically wrinkles, with an improved method of correlating ultrasonic test data to actual anomaly characteristics.
There is a also known procedure of planning a sequence of repair and renovation steps to be applied to the defective segments of heating infrastructures and buildings (RU 2110011 C1 (21) 95112182 (22) 13 Jul. 1995 published 27 Apr. 1998). This method offers Infra-red imaging of the constructions under testing, defining the defective areas, digitizing their images and evaluating the excessive heat produced by defective areas. The resulting data leads to the planning of a sequence of steps required for repairs.
The disadvantage of this method is a limited area of application where the heat-transferring objects, such as heating infrastructure, are present. Moreover, this method is effective only at the stage when the fracture and leakage have already been developed, causing the excessive heat radiation around the defective areas.
There are several techniques for non-destructive testing of pipes that have been known. Thus, US20060283251 (Hunaidi) suggests non-destructive condition assessment of a pipe carrying a fluid by evaluating the propagation velocity of an acoustic disturbance between two remote points on the pipe. A corresponding predicted value for the propagation velocity is computed as a function of the wall thickness.
Another non-destructive technique U.S. Pat. No. 4,641,529 (Lorenzi, et al) discloses pipeline ultrasonic transducers in combination with photographic device for corrosion detection. Such ultrasonic transducer(s) produce a parallel beam for direction toward the pipe wall from inside a pipe, with a sufficiently large beam width to permit comparison of time displayed signal components in defect depth determination, with the signal propagating through a gaseous medium.
There is another method for estimating worst case corrosion in a pipeline is disclosed in U.S. Pat. No. 7,941,282 (Ziegel, et al), in which non-destructive pipeline wall thickness measurements are performed by sampled (at locations) ultrasonic and/or radiography (UT/RT) measurements. A distributed ILI data library for test pipelines is calibrated to correspond to UT/RT measurements for inspection. After sampling, the candidate statistical distributions are evaluated to determine which of the candidate most accurately estimates the worst case corrosion measured by ILI.
There is a known method for repair sequence planning based on possible (metal pipe) defects location and cause discovering by detecting anomalies in the magnetic field of pre-magnetized pipeline with special devices, such as pig-flow defectosopes, (RU No 2102652, 6F 17D5/00, published 1998).
Such a method includes a pipe-line setup with defectosope input-output chambers and a pig-flow device itself, as well as internal pipe-line surface cleaning means to provide the open cross-section needed to launch the pig-flow device. The method also requires a simultaneous magnetization of the pipe-wall along the pig-flow device movement and registration of anomalies based on scattering and saturation of the magnetic field, recording and processing of the information to conclude about defects location and nature.
As an example, another method can also be considered: RU2139515 filed Dec. 23, 1997. This method of evaluation of the material vulnerability and residual operation resource relies on the measured dependence between the mechanical (structural) defects (related to steel resistance) and steel parameters measured by non-destructive means, such as value of magnetic permeability measurement.
The Pipeline Defect Assessment Manual (PDAM) was issued in 2003. It is the first document that provides the pipeline industry with best practices for the assessment of a wide range of pipeline defects. In addition, guidance is given on the treatment of the interaction between defects (leading to a reduction in the burst strength), and the assessment of defects in pipe fittings (pipe-work, fittings, elbows, etc.). Guidance is also given on predicting the behavior of defects upon failing, including both leak or rupture, and fracture propagation. PDAM broadly follows the following format for each defect type and assessment method: 1. A brief identification of the defect's type. 2. A figure illustrating the dimensions and orientation of the defect relative to the axis of the pipe, and a nomenclature. 3. Brief notes that highlight particular problems associated with the defect. 4. A flow chart summarizing the assessment of the defect. 5. The minimum required information to assess the defect. 6. The assessment method. 7. The range of applicability of the method, its background, and any specific limitations. 8. An appropriate model uncertainty factor to be applied to the assessment method. 9. An example of the application of the assessment method. 10. Reference is made to alternative sources of guidance available in national or international guidance, codes or standards.
The, the technological outcome of present invention would include:
1) Expanding the implementation area, including not only the heating infrastructure and buildings but also various types of extended structures of metallic materials, including not-through defects in stage of development.
2) Increasing the reliability and accuracy of information about repair procedures suggested schedule. It can be done using the risk-factor ranking tables based on the absolute values of stress, compared against the values from regulatory documentation (for particular object).
3) Increasing the efficiency of the method by applying a visualization-assisted maintenance and repair schedule (with the real values of mechanical stress) to the actual structural layout, such as a pipe-line integrated into the existing topology, for example.
Such technological outcome can be achieved, mainly, due to the following innovative means: i) Remote (from the ground surface, non-destructive) identification of the defects and their respective risk-factors, by using improved measurements of the local mechanical stresses; ii) Remote identification of operational parameters for the defective segments of the structure, by using the absolute local stress values, compared against the values from regulatory documentation (for particular object). iii) Graphical visualization of the obtained information using the actual topological layout of the area and the structure in absolute geographical coordinates.